The present invention relates to a superconducting tape or wire produced by the wire-in tube method. Superconducting tapes and wires are principally made by the well known powder-in tube (PIT) method. It is heretofore been suggested that a wire-in tube (WIT) method be employed using one or more strands of wire in the tube prior to introducing the superconductor powder into the tube. Thereafter, the manufacturing of the tape or wire follows the same manufacturing process as the-traditional PIT, that is calcining, annealing and sintering steps are used in conjunction with mechanical swaging or drawing to provide the final tape.
This invention revolves around the discovery that wire-in tube tapes have shown little, if any, improvement over traditional PIT tapes except if certain specific superconducting powder or precursors thereof are used. The powders which form the basis for the invention are reported in U.S. Pat. No. 5,523,285 issued Jun. 4, 1996 to Balachandran et al. which describes therein the freeze dried preparation of Pb-doped Bi.sub.2 Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.x (2223) which more specifically is Bi.sub.1.8 Pb.sub.0.4 Sr.sub.2.0 Ca.sub.2.2 Cu.sub.3.0 O.sub.y where y is between 10 and 11. The freeze dried powders used in the present invention may be either crystalline or non-crystalline or mixtures thereof.